In a polishing technique, there has been required that damages to an under layer are suppressed while an adequate polishing rate is secured.
For example, in late years, in a process of forming an interconnect in the manufacture of semiconductor devices, as a technique for forming a trench for forming the interconnect on an insulating film, embedding a metal film for the interconnect in the trench by the plating method, removing an excess metal film and smoothing the insulating film including metal interconnect, CMP (Chemical and Mechanical Polishing) has been used. This is a method of mechanically polishing a polished surface which is chemically deteriorated by a slurry with abrasive particles dispersed therein.
A CMP process is an essential process in the processing of insulating film materials such as silicon oxide and the like as well as metallic materials such as a copper interconnect, a tantalum barrier metal, a tungsten plug and the like. In the future, however, in order to reduce the cost involved in the process, it has been demanded that a high polishing rate is obtained just with a little supply of slurries, and damages to the under layer hardly take place. As damages to the under layer in CMP, there can be exemplified scratch, dishing and erosion.
Of such damages, scratch refers to abrasive damages on a metal surface, and is created by the hardness of abrasive particles or the partial excessive polishing generated by the existence of an aggregate of abrasive particles.
Furthermore, dishing or erosion causes an increase or deviation in interconnect resistance and a short circuit between interconnects formed on an upper layer, thereby considerably deteriorating the reliability of devices having an interconnect structure and drastically lowering the product yield.
Of these, erosion is a phenomenon of forming concave portions by further polishing an object to be polished including an insulating film, i.e., an under layer as well in the center of a dense area of an interconnect pattern. Erosion is caused by excessive polishing due to hard abrasive particles or a low polishing selectivity with an insulating film or an under layer such as a barrier layer for preventing diffusion of a metal.
Furthermore, dishing is easily caused by elution (etching) of a metal due to a slurry in the acidic range that is the corroded region of a metal, a complex forming agent contained in the slurry or a pH adjusting agent. Furthermore, a slurry having a stronger chemical reactivity because of an additive than a mechanical reactivity because of abrasive particles easily causes dishing.
In the CMP technique, a slurry containing a metal oxide such as ceria, alumina or the like, or an inorganic abrasive particle such as silica has been used from the past. However, these inorganic abrasive particles have high hardness, and aggregates of abrasive particles or polished debris in liquid waste are hardly discharged. So, when a metal film with low hardness such as copper or the like is polished, the aforementioned scratch or erosion might occur in some cases.
That is, at present, in order to improve performance of semiconductors, the ½ width of interconnects (half pitch) on an insulating film becomes much finer from 90 nm to 65 nm and even to 45 nm, and a surface of the insulating film to be polished is of a much complicated structure. If the width of interconnects becomes much finer, abrasive damages to the metal surface due to scratches cause an open circuit, and erosion causes an increase or deviation in interconnect resistance and a short circuit between interconnects formed on an upper layer, thereby considerably deteriorating the reliability of semiconductor devices and drastically lowering the product yield.
In order to solve these problems, in case of inorganic abrasive particles, a polishing solution with abrasive particles composed of silica which is softer than alumina and polishing in a neutral to alkaline range without causing elution of a metal by forming a passive film of a metal has been under development. For example, when silica is used as abrasive particles, scratches are reduced as compared to alumina. However, when inorganic abrasive particles are used, a metal is mechanically polished so that scratch or erosion occurs due to aggregates of abrasive particles or polishing debris of the metal and occurrence of defects cannot be thoroughly prevented.
Furthermore, the conventional polishing techniques are described in Patent Documents 1 to 10.
In Patent Documents 1 and 2, in order to effectively use the supplied slurry, optimization of trench patterns on a polishing pad has been studied.
Meanwhile, in Patent Document 3, there has been disclosed a method employing particles of an organic polymer compound as abrasive particles. Examples of the organic polymer used therein include a methacrylic resin, a polystyrene resin and the like.
However, these organic polymers do not have functional groups which easily react with a metal film. In the same document, since these components are used as abrasive particles and the organic polymers do not contain an oxidizing agent for oxidizing a surface of the metal, a chemical action with the metal film to be polished never takes place. Thus, a sufficient polishing rate required for an interconnect process in the manufacture of semiconductor devices is not obtained.
Meanwhile, in order to solve the above problems on particles of the organic polymer compound, for example, in Patent Document 4, there has been disclosed an aqueous dispersion for polishing containing organic particles having functional groups capable of reacting with a metal forming a surface to be polished. However, also in the art described in the same document, a phenomenon called dishing of forming concave portions by further polishing a metal film of an interconnect portion in the center has not been solved.
Further, in Patent Document 5, there has been disclosed a polishing slurry containing a chelating resin and inorganic abrasive particles.
Further, in Patent Documents 6 and 7, there has been disclosed a polishing liquid for CMP containing a polyacrylic acid for the purpose of reducing dishing by suppressing etching.
Further, in Patent Documents 8 and 9, there has been described a polishing agent for CMP containing a protective film-forming agent and a water-soluble polymer.
Further, in Patent Document 10, there has been described a polishing slurry combining suppression of etching and a high polishing rate by forming a brittle insoluble metal complex using a complex forming agent such as a quinolinecarboxylic acid or the like.
However, even though these techniques are used, they have been further improved from the viewpoint of suppressing damages to an under layer while securing a more adequate polishing rate.
Patent Document 1: Japanese Patent Laid-open No. 1999-216663
Patent Document 2: Japanese Patent Laid-open No. 1999-333699
Patent Document 3: Japanese Patent Laid-open No. 1995-86216
Patent Document 4: Japanese Patent Laid-open No. 2001-55559
Patent Document 5: Japanese Patent Laid-open No. 2002-261052
Patent Document 6: Japanese Patent Laid-open No. 1999-195628
Patent Document 7: Published Japanese Translations of PCT International Publication for Patent Applications No. 2004-532521
Patent Document 8: International Publication (WO) No. WO00/13217, pamphlet
Patent Document 9: International Publication (WO) No. WO01/17006, pamphlet
Patent Document 10: Japanese Patent Laid-open No. 2000-183003